Acid mine drainage or acid rock drainage (interchangeably referred to herein as ARD) results from the penetration of oxygen into waste rock that contains ferrous sulfides (pyrites), with the consequent conversion of the sulfites to sulfuric acid. ARD is the outflow of acidic water into the environment, usually from disturbed earth such as mines or large construction sites that contain pyrite and other iron-containing ores. The acidity and precipitation of metal solids disrupts stream ecosystems and kills plant and animal life. Sulfuric acid, produced from the interaction of the water with the rock, extracts additional iron-containing compounds from the waste rock and causes pollution of the affected streams often for miles below the source of the pyrite. Broken rock that occurs from mining and construction activities is especially susceptible to ARD, as the iron and metallic compounds in the exposed areas of the fractured rock may oxidize and be carried away by water that passes over the rock.
The methods and systems described in this document are directed to the prevention of ARD.